| Location in body, and variable functions.
Size and shape of cells: spindle-shaped; large surface area/volume ratio.
Internal structure: sarcoplasmic reticulum; organization of contractile
filaments; thick, thin and intermediate filaments, dense bands and dense
bodies. Activation through Ca2+ and myosin light chain kinase.
Arrangement of cells into bundles, cell-to-cell connections. Neural and
chemical activation. |
Types of smooth muscle as judged from methods
of activation.
(i) electrically excitable, activated entirely through nervous activity
(vas deferens, arterioles); (ii) spontaneous electrical activity modulated
through nervous activity-pacemaker depolarizations and spikes (bladder,
some gut muscle) or basic slow wave activity (most gut, uterus); (iii)
electrically inexcitable, activation through pharmaco-mechanical coupling
using second messengers only (respiratory tract, many blood vessels).
Underlying mechanisms.
Patterns of innervation. |